Indiana Administrative Code
Title 675 - FIRE PREVENTION AND BUILDING SAFETY COMMISSION
Article 30 - INDIANA BOILER AND PRESSURE VESSEL RULES
Rule 10 - Existing Installations of Heating Boilers
Section 10-13 - Relief valves for hot water heating or supply boilers; settings; dimensions; relief capacity

(a) Each hot water heating or hot water supply boiler shall have one (1) or more relief valves of the spring-loaded type without disk guides on the pressure side of the valve. The valves shall be set to relieve at a pressure at or below the MAWP of the boiler and so arranged that they cannot be reset to relieve at a pressure higher than the MAWP of the boiler. The capacity of water relief valves that have not been officially rated in accordance with the ASME B&PVC shall not be taken into consideration in determining the required relieving capacity.

(b) Each relief valve shall have a substantial device that will positively lift the disk from its seat at least one-sixteenth (1/16) inch when there is no pressure on the boiler.

(c) The seats and disks of relief valves shall be of material suitable to resist corrosion and withstand the preliminary test prescribed in the ASME B&PVC for low pressure heating boilers. No materials liable to fail due to deterioration or vulcanization when subjected to any temperature not exceeding two hundred seventy-five (275) degrees Fahrenheit shall be used for any part.

(d) No relief valve shall be smaller than three-fourths (3/4) inch nor larger than four and one-half (41/2) inches standard pipe size. The inlet opening shall have an inside diameter equal to, or greater than, the seat diameter. In no case shall the minimum opening through any part of the valve be less than one-fourth (1/4) inch diameter or its equivalent area.

(e) The relieving capacity in pounds per hour shall be determined from the maximum Btu output at the boiler nozzle obtained by the firing of any fuel for which the unit is designed. In many cases a greater relieving capacity than the minimum specified will be necessary. In every case, the requirements of subsection (g) shall be met.

(f) When operating conditions are changed or additional boiler heating surface is installed, the valve capacity shall be increased, if necessary, to meet the new conditions and be in accordance with subsection (g). The additional valves required by changed conditions may be installed on the outlet pipe providing there is no intervening valve, nor any other branching pipes between valve and boiler.

(g) Relief valve capacity for each boiler shall be such that with the fuel-burning equipment installed, pressure cannot rise more than twenty percent (20%) above the highest maximum allowable working pressure for pressure up to and including thirty (30) psig and ten percent (10%) for pressures over thirty (30) psig.